This invention relates to an improved process for preparing a vanadyl phthalocyanine composition. More specifically, this invention is directed to the synthesis and treatment of vanadyl phthalocyanine to achieve a material with superior electrophotographic properties.
Phthalocyanines in general and vanadyl phthalocyanine in particular have been described in the prior art as useful materials in electrophotographic devices. The use of phthalocyanines as photogenerator material in simple or complex electrophotographic devices is of particular interest as their photosensitivity extends from the visible region to the infrared, thus rendering them suitable for use both in conventional electrophotographic copiers and duplicators, as well as in infrared diode laser and light emitting diode (L.E.D.) based printers.
The usefulness of a photogenerator pigment such as vanadyl phthalocyanine is greatly enhanced if the pigment composition possesses a superior set of electrophotographic properties. Various characteristics of copiers, duplicators or printers, such as hardware complexity, cost, operating speed, copy or print quality, photoreceptor life, and the like, can all be impacted by the quality of the photogenerator material. It is well known to those skilled in the art that materials which seem to be identical, when examined and compared using the most elaborate physical or chemical analytical procedures, can quite often exhibit markedly different electrophotographic properties.
The preparation of vanadyl phthalocyanine is described in the open and patent literature both in terms of synthetic alternatives or typical sulfuric acid treatments used in the dye and pigment industry. Preparation methods for vanadyl phthalocyanine specifically for electrophotographic use are disclosed in U.S. Pat. No. 4,508,650 and U.S. Pat. No. 4,557,868.